Radio Shack EC-490 Handheld Electronic Calculator

The 1976 Radio Shack catalog advertised this handheld electronic calculator as “our finest scientific slide-rule calculator.” At a list price of $99.95, it was described as “a superb buy.” The calculator has a tan, black, and brown plastic case with an array of twenty-five sloping plastic keys. These include ten digit keys, a decimal point key, a pi key, four arithmetic function keys, a total key, an exchange key, and two parentheses keys. The top row of keys includes a clear entry/clear key, an EE (enter exponent) key, a change sign key, a function key, and an ARC key.
Many of these keys had a different effect if the F or ARC key was pushed. Functions found in this way include inverses, exponents, powers, logarithms, square roots, trigonometric functions, inverse trigonometric functions, conversion from radians to degrees, conversion from degrees to radians, and factorials. The calculator also has memory keys. Behind the keys are a degree/radian switch and an on/off switch. Behind the switches is a twelve-character vacuum fluorescent display that shows results in scientific notation, including eight digits of the result, two digits of the exponent in base ten, and the sign of both the number and the exponent. The back edge of the calculator has a jack for a power supply.
A sticker on the back describes operating procedures. Text near the bottom reads: RADIO SHACK A TANDY CORPORATION COMPANY (/) FORT WORTH, TEXAS 76107. Further text reads: Calculator Model EC-490 (/) Catalog Number 65-635 (/) Assembled in Mexico. A further mark reads: Ser. No. (/) 108809.
The calculator has an imitation leather carrying case. Text on the front reads: Radio Shack.
Compare this device to calculator 1986.0988.163, a Rockwell 63R.
Radio Shack, A Tandy Company, 1976 Electronics Catalog , p. 117, accessed September 22, 2014, at
Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 121.
Currently not on view
date made
Tandy Corporation
place made
Physical Description
plastic (case; carrying case; keys material)
metal (trim; circuitry material)
paper (sticker material)
overall: 1 in x 3 3/8 in x 6 in; 2.54 cm x 8.5725 cm x 15.24 cm
ID Number
catalog number
accession number
Credit Line
Gift of John B. Priser
See more items in
Medicine and Science: Computers
Handheld Electronic Calculators
Computers & Business Machines
Data Source
National Museum of American History, Kenneth E. Behring Center


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